1. Field of the Invention
The present invention relates to pumping apparatus and, more particularly, to an improved method and apparatus for continuously pumping powdered materials without bridging or packing in either the material hopper or in the pumping cylinder or sleeve.
2. The Prior Art
It is well known that powdered materials, when pushed through a cylinder by a piston, tend to bridge, pack, or form a plug. It is then necessary to break the bridge, loosen the packed material or remove the plug before pumping can be resumed. Further, with prior devices, when pumping the powdered material into a pressurized vessel, as soon as the pumping chamber has been filled and the discharge valve is opened, the end of the pumping chamber is placed in direct communication with the pressurized vessel. The pressure from the vessel tends to act the same as a moving piston and produces a plug in the pumping chamber, thereby creating discharge problems.
Other prior devices seek to transport the powdered material through conduits, using compressed air as the carrier, but such devices are prone to pack and clog. Still others mix the powdered material with a liquid medium to provide a slurry that can be pumped, but these are unsatisfactory for use in installations in which it is desired to use the powdered material in a loose dry form.
The foregoing objections and disadvantages are avoided by the present method and apparatus, which embodies "fluidization" of the powdered material in the hopper and provides novel means for forming a void in entrapped powdered material before discharging it, as will be described more fully hereinafter.
The terms "fluidize," "fluidizing" or "fluidization," as used herein, mean subjecting the powdered material to the action of gas or air to suspend the powdered particles and to reduce and maintain its density in the hopper fairly constant.